The invention relates to the treatment of and immunization against spontaneous and viral-induced infections, bacterial or parasitic infections, proliferative diseases and inflammatory diseases. More specifically the invention relates to the use of metal chelating materials including, picolinic acid, fusaric acid and their derivatives as chemotherapeutic and/or biological response modifier agents.
It will be appreciated that hereinafter the use of the term "response modifer" is intended to encompass all of the intended functions of the invention and method including antiviral, antiinfective, antiinflammatory, anticancer, vaccine and so on. Further, it will be appreciated that the broad term "antiinfective" is intended to include antibacterial, antifungal, antiparasitic functions, as well as actions against any other infective agent including viruses not encompassed by the term "antiviral".
Researchers recently have come to appreciate the role of metal containing proteins in proliferative and infectious diseases. Generally speaking, the inventor has studied the important function of proteins having amino acid sequences which bind metals, particularly transition metal ions therein. For example, the inventor has determined the important role zinc finger or zinc ring proteins in proliferative, inflammatory and infectious diseases.
The inventor and others have recognized at least three efficient approaches to inhibiting zinc finger proteins: 1) disruption of the zing finger by modification of the cysteins which are at least one of the four binding sites for Zn.sup.2+ in the zinc finger protein which results in the ejection of zinc ion; 2) removal of the zinc from the zinc finger moiety by specific chelating agents; and 3) specific chelating agents that form a ternary complex at the site of zinc binding on zinc finger proteins, resulting in inhibition of the DNA or RNA binding activity of zinc finger proteins.
Papilloma virus infection results in a number of proliferative diseases in subjects including warts induced by type 4 human papilloma virus (common warts). Moreover, papilloma virus can cause plantar ulcers as well as plantar warts. Human papilloma virus infection of the uterine cervix is the most common of all sexually transmitted diseases. Commonly know as genital warts, this wide spread virus infection is a serious disease that potentially can develop into cervical cancer. Since the virus is permanently present in cells, infection recurs in a significant percentage of patients. In many instances, conization of the uterine cervix is required to remove the infected tissue.
Condylomata acuminata, also denoted genital warts, are benign epithelial growths that occur in the genital and perianal areas and caused by a number of human papilloma viruses (HPV) including types 6,11 and 54. These are low risk viruses which rarely progress to malignancy. However, high risk viruses such as HPV-16 and HPV-18 are associated with cervical intraepithelial cancer.
The actions of HPV are mediated by specific viral-encoded proteins which interact and/or modulate cellular DNA and proteins to produce abnormal growth and differentiation of cells. Two proteins of the HPV viral genome, E6 and E7, are well conserved among anogenital HPV's and both may contribute to the uncontrolled proliferation of basal cells characteristics of the lesions. The E7 oncoprotein is a multi-functional protein with transcriptional modulatory and cellular transforming properties. The E7 oncoprotein is denoted as a "zinc finger" protein because it pocesses a sequence motif that is implicated in zinc binding. A strong correlation between zinc binding and the transactivation activity of E7 has been documented. The HPV-16 E6 protein is a "zinc finger" protein that binds DNA and may have transcriptional properties such that its function may be dependent upon the formation of zinc fingers. E6 protein can complex with the cellular tumor suppressor protein p53 and it is necessary with E7 protein for the immortalization of primary human squamous cells. Only two proteins of HPV are consistently expressed and integrated in keratinocytes, the E6 and E7 zinc finger proteins. The E6 and E7 proteins are responsible for continuous cell proliferation. About twenty HPVs are associated with ano-genital lesions and all transformed keratinocytes of these lesions contain E6 and E7 zinc finger proteins. The E6 and E7 regulate growth and transformation by interfering with cellular p53 and pRb proteins, respectively. Thus, one should be able to control or cure HPV by inactivating E6 and E7, the critical zinc finger proteins which are required for replication. When replication of the virus is halted, apoptosis of the virally-infected cells must occur. Thus, one can alter the epidemiology of, for example, carcinoma of the uterine cervix by interfering with the function of zinc finger or zinc ring proteins.
The human immunodeficiency virus (HIV) encodes several regulatory proteins that are not found in other retroviruses. The tat protein, which is one of these proteins, trans-activates genes that are expressed from the HIV long terminal repeat and tat is essential for viral replication. The tat protein of the HIV-1 is a zinc finger protein that when added to certain cells in tissue culture, specifically promotes growth. It has been shown that the tat protein of HIV-1 stimulates growth of cells derived from Kaposi's sarcoma lesions of AIDS patients. Other experiments raised the possibility that tat might act as a viral growth factor to stimulate replication in latently infected cells or alter expression of cellular genes.
The nucleocapsid p7 protein of HIV has been targeted by the inventor for treatment of HIV viral infections. The p7 protein is required for the correct assembly of newly formed virus particles during the viral life cycle. Moreover, the p7 protein contains two zinc fingers that are required for the recognition and packaging of the viral RNA. Because the zinc finger domain is essential for nucleic acid binding, p7 resistant mutants are highly unlikely to occur. Thus, agents that effectively attack the two zinc finger domains of the HIV virus nucleocapsid p7 in vivo will decrease the overall number of viral particles that bud off and exit the cells to infect other cells.
Further, the hepatitis C viruses are dependent upon the Zn 2+ metalloproteinases for specific viral functions.
It is of interest to note that the breast cancer susceptibility gene BRCA 1 includes a zinc ring domain that are involved in protein-protein interactions or protein-DNA interactions.
It also is of interest to note that the zinc ring domain of the BRCA 1 has a 54% sequence similarity and 38% sequence identity with a zinc ring domain encoded by the genome of the equine herpes virus. (R. Bienstock, "Molecular Modeling of Proteins Structures, Science & Medicine, January/February 1997, p.56).
From the foregoing it appears that it would be beneficial to have a product that can interfere with the formation or action of certain zinc finger proteins or zinc ring proteins to stop the progress of certain virally induced or mediated proliferative diseases or to halt the progress of viruses or malignancies dependent upon zinc finger or zinc ring proteins for their transformation and immortalization. Furthermore, it would be beneficial to provide a product that can halt the growth of other proliferative cells, such as malignant cells by chelating metal ions from zinc-dependent or transition metal ion (e.g. copper, iron, etc.) dependent proteins and enzymes necessary for the replication of the malignant cells.